1. Field of the Invention
The present invention relates to a low-cost vibration-suppressing cutting tool that can significantly reduce chatter vibrations mainly in cutting operations in which chatter vibrations cause problems.
2. Description of the Background Art
It has been well known that chatter vibrations can be suppressed by a method that uses inertia by incorporating a damper or similar member into a holder. In particular, in a boring bar for cutting an inside diameter, the size of the holder is limited by the hole diameter of a workpiece. Consequently, the amount of over-hang must be increased by using a slender shank. This structure tends to generate chatter vibrations. As a result, the prior art on the vibration-suppressing cutting tool mainly relates to a boring bar. Therefore, the following explanation is made by mainly referring to the boring bar as an example.
For example, the published Japanese patent application Tokukai 2003-136301 has disclosed the following method. As shown in FIGS. 5A and 5B, a hole 21 is drilled from the rear end of a shank portion 2 of the holder. A damper 22 is inserted into the hole 21 to place it at the tip portion of the holder near the cutting corner. A bar-shaped core 23 made of cemented carbide is inserted into the remaining portion of the hole 21. Another published Japanese patent application, Tokukaihei 6-31507, has disclosed a vibration-suppressing cutting tool in which a deep hole is formed at the center portion of the holder to house a weight.
As described above, an example of the conventional vibration-suppressing cutting tool has a deep hole drilled in a long holder to insert a damper so that it can be placed at the deepest portion of the hole. This structure increases the machining cost for producing an inside diameter-cutting holder, in particular, which has a long, small-diameter shank, because the hole must be drilled by using a gun drill or the like. Another example of the conventional vibration-suppressing cutting tool has a large hollow portion for inserting the weight of the damper. This structure decreases the stiffness of the holder. In addition, the complicated structure poses a problem of increasing the cost.
In addition, the complicated structure of these holders also poses the following problems: (a) the diameter of the shank of the holder is limited, and therefore the cutting diameter of the inside-diameter cutting is limited, and (b) the cutting condition to achieve the vibration-suppressing effect is limited.